The present invention relates to a process for manufacturing a DC superconducting quantum interference device ("DC-SQUID"), which is applied to a highly sensitive magnetic sensor, an ammeter, a displacement meter, a high-frequency signal amplifier or the like.
The steps of the prior art are shown in sections in FIGS. 2(a) to 2(e). These steps manufacture a SQUID integrated with a pick-up coil and begin fabricating a pick-up coil 1, a feedback coil 2 and an input coil 3 before the remaining steps. The individual steps will be briefly described in the following. FIG. 2(a) shows a step at which the surface is flattened with the first insulating film 4 after the pick-up coil 1, the feedback coil 2 and the input coil 3 are formed of a superconducting film. This superconducting film is formed by depositing Nb by sputtering, and the first insulating film 4 is flattened by applying SOG after SiO.sub.2 has been deposited by plasma CVD.
FIG. 2(b) shows a step at which a resistance film 5 for shunting or damping the SQUID is set to a designed value by a second insulating film 6 after it has been deposited. The resistance film 5 is made of Pd, and the second insulating film 5 is formed by evaporating MgO together.
FIGS. 2(c) and 2(d) show steps at which a Josephson junction 10 and a washer coil 11 are fabricated. The Josephson junction 10 is formed by depositing a Nb/Al-oxide/Nb structure by sputtering. The washer coil 11 is formed of a lower electrode 7 of the Josephson junction 10.
FIG. 2(e) shows a step at which an opposed electrode 13 of a superconducting film is formed after a third insulating film 12 has been deposited. The third insulating film 12 and the counter electrode 13 are deposited together, respectively, by evaporating SiO and PbIn.
According to the steps of FIG. 2, the pick-up coil 1, the feedback coil 2 and the input coil 3 are fabricated before the remaining steps so that the number of masks for patterning the deposited films by a photolithography increases. Since the number of steps increases, the time for the manufacture is elongated to reduce the production yield of the element.